package com.supreme.secretserver.utils;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Base64;
import java.util.Map;

public class RSATestUtils {

    public static final String KEY_ALGORITHM = "RSA";
    public static final String PUBLIC_KEY = "RSAPublicKey";
    public static final String PRIVATE_KEY = "RSAPrivateKey";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    public static String publicKey = "MFwwDQYJKoZIhvcNAQEBBQADSwAwSAJBAKzScQr1M6hWWiwNzwraVFoMxxHrGLR3Xr144hUOGCg46IkaSrriVL5BACQJ5Z1P43k+McshEpkOKSpOXFcJkNkCAwEAAQ==";
    public static String privateKey = "MIIBVgIBADANBgkqhkiG9w0BAQEFAASCAUAwggE8AgEAAkEArNJxCvUzqFZaLA3PCtpUWgzHEesYtHdevXjiFQ4YKDjoiRpKuuJUvkEAJAnlnU/jeT4xyyESmQ4pKk5cVwmQ2QIDAQABAkEAjFo7xBJu6X93q99rDf1SE+/cnAi5/5YSMv5BXagcpkx60ImxPRGG0NIeMb0WxShbT/5J7kJzW7ufceg20BFCoQIhAOGddY8sFiU/Nyhyt+37CnzQ2a+vCimvpUL4A1BWqOnjAiEAxBjVoXme9EQVlVYl3joc60EbiwPTpBTvLNsGUfRpBxMCIQCB7do735nJTYSIaLh/9ujtRKF4yYdCxoKX9JiD9cRFHQIhAIR8mukr+H7j+QkaWR9Zd+xh4q/7d+Ql2KofmJeKX+NNAiBcXRtcvtsIeIWTTFwMFBhaO8y0CEAXJ0JJBSDLU+SRaQ==";

    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 2048;

    //获得公钥字符串
    public static String getPublicKeyStr(Map<String, Object> keyMap) throws Exception {
        //获得map中的公钥对象 转为key对象
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        //编码返回字符串
        return encryptBASE64(key.getEncoded());
    }


    //获得私钥字符串
    public static String getPrivateKeyStr(Map<String, Object> keyMap) throws Exception {
        //获得map中的私钥对象 转为key对象
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        //编码返回字符串
        return encryptBASE64(key.getEncoded());
    }

    //获取公钥
    public static PublicKey getPublicKey(String key) throws Exception {
        byte[] keyBytes = Base64.getDecoder().decode(key);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PublicKey publicKey = keyFactory.generatePublic(keySpec);
        return publicKey;
    }

    //获取私钥
    public static PrivateKey getPrivateKey(String key) throws Exception {
        byte[] keyBytes = Base64.getDecoder().decode(key);
        PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
        return privateKey;
    }

    //解码返回byte
    public static byte[] decryptBASE64(String key) throws Exception {
        Base64.Decoder decoder = Base64.getDecoder();
        return decoder.decode(key);
    }


    //编码返回字符串
    public static String encryptBASE64(byte[] key) throws Exception {
        Base64.Encoder encoder = Base64.getEncoder();
        return encoder.encodeToString(key);
    }

    //***************************签名和验证*******************************
    public static byte[] sign(byte[] data, String privateKeyStr) throws Exception {
        PrivateKey priK = getPrivateKey(privateKeyStr);
        Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);
        sig.initSign(priK);
        sig.update(data);
        return sig.sign();
    }

    public static boolean verify(byte[] data, byte[] sign, String publicKeyStr) throws Exception {
        PublicKey pubK = getPublicKey(publicKeyStr);
        Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM);
        sig.initVerify(pubK);
        sig.update(data);
        return sig.verify(sign);
    }

    //************************加密解密**************************
    public static byte[] encrypt(byte[] plainText, String publicKeyStr) throws Exception {
        PublicKey publicKey = getPublicKey(publicKeyStr);
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        int inputLen = plainText.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        int i = 0;
        byte[] cache;
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(plainText, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(plainText, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptText = out.toByteArray();
        out.close();
        return encryptText;
    }

    public static byte[] decrypt(byte[] encryptText, String privateKeyStr) throws Exception {
        PrivateKey privateKey = getPrivateKey(privateKeyStr);
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        int inputLen = encryptText.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptText, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptText, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] plainText = out.toByteArray();
        out.close();
        return plainText;
    }
}
